Robert Colvile is a writer and senior comment editor at the Telegraph, who cares more about politics and policy than is probably healthy - for his newest pieces, please see here. He tweets as @rcolvile.

It's not that the personal doesn't spill into the political over here as well – for a decade, the course of government has been determined by conflicting accounts of what Tony said to Gordon at Granita. But this is a whole different league. The only way we could have got close would have been if Cherie had been chair of the Labour Party while Tony was PM, or if Gordon had married Margaret Beckett or Patricia Hewitt (and God, think of the poor children from either liaison).

But the Royal/Hollande split says something else about France. Think of America's equivalent power couple, Bill and Hillary Clinton. Hillary's Senate run was based on standing by her man – it's unimaginable that she could have divorced Bill, and run against him for office, without destroying both of their political careers.

In France, by contrast, they just shrug their shoulders – not only were Royal and Hollande running an election campaign while their relationship was falling apart, but they weren't even married. We might dislike this laissez-faire attitude, but – according to a piece in the Economist - it could be what saves Europe from demographic disaster.

Recently, many commentators have become convinced that the continent is doomed to insignificance as its population declines, swamped by the fast-breeding Muslim hordes. Mark Steyn, for example, used to write along these cheery lines in the Telegraph.

The Economist piece tells a subtler tale. Yes, there are countries where the demographic situation looks grim – Spain, Italy and Germany, for example. But in others, including Britain but most especially in France, numbers of births are curving back up towards replacement rates, even without the help of immigration (and first-generation immigrants' greater propensity for childbearing).

Of course, there is an issue the piece does not address, which is that such children may be more numerous than their Mediterranean peers, but could well be worse-off. Study after study has shown that long-term, committed, stable relationships are the best for children's development – in other words, marriage, or something very close to it. Yet all attempts to mimic America's demography, in which the traditional family unit is powering along, have failed on this side of the Atlantic.

Having more children if you cannot offer them a stable home might be great for demography, but bad for society – and for the children themselves. The inescapable, although rather nasty, logic is that European countries are faced with an unappetising choice about the next generation: quality or quantity?